Debris filter with filter screen in the form of a spherical section

ABSTRACT

A debris filter has a housing, a filter screen mounted to the housing and disposed so as to extend across a flow path through the housing, a debris extractor mounted to the housing, and a splitter bar also mounted to the housing. The debris extractor and the filter screen are so mounted to the housing as to enable rotation of the filter screen and the debris extractor relative to one another. The debris extractor has a debris intake opening and the debris extractor and the splitter bar are so mounted to the housing that the intake opening is positionable adjacent to or in juxtaposition with the splitter bar with the splitter bar overlapping and shielding the intake opening.

FIELD OF INVENTION

This invention relates to a debris filter with rotatable debrisextractor. In addition, this invention provides a system and a method ofoperating a debris filter.

BACKGROUND OF THE INVENTION

Thermal and nuclear power plants use steam condensers for condensationof steam after the energy has been utilized to drive the turbine(s). Thesteam condensers may be water-cooled or air-cooled. In water-cooledprocess, water is typically obtained from sources like sea, rivers andlakes. The quantity of water required is quite large and it containsdebris like grass, shells, fish, cloth and plastic sheet material. Suchdebris tends to clog the tubes of the steam condensers, causingreduction in heat transfer, which in turn may affect power generation.The problem of accumulation of debris and the need for periodic removalof debris poses a serious challenge to the power generating plants. Toovercome this problem, an automatic debris filter is installed at theinlet of the condenser, which filters and removes suspended particles.Conventional automatic debris filters use different techniques forremoving debris. In one such conventional debris filter, a tubularhousing and a screen basket are provided, the screen basket beingfastened to an inner periphery of housing. In the general arrangement ofthe debris filter, a debris extraction arm is mounted on the inlet sideof the basket and is rotatable with respect to the screen and on itscomplete surface area.

For dislodging and removing debris clogged on the screen suction arms,which completely closes a segment of the screen and is rotatable tocover the complete screen, another method was adopted in the prior artis to use a debris filter with a rotatable suction arm inside the basketarm along with a jet water spray arrangement positioned outside thescreen. In this debris filter the profile of the debris extractor doesnot facilitate removal of sticky debris from the screen easily. Hence,an additional water spray pump which delivers water at a velocity morethan the inlet velocity of water from the clean side of filter isrequired to reverse the sticky debris from the screen. This arrangementresults in additional power consumption for the water spray pump andalso makes it more expensive.

OBJECTS OF THE INVENTION

An object of the invention is to provide an improved debris filter witha rotatable debris extractor.

A further object of the present invention is to provide a debris filterthat is more efficient than conventional filters and occupies less spacefor the same throughput.

Another object of the present invention is to provide a debris filterthat is less expensive than conventional debris filters.

These and other objects of the invention will be apparent from thedrawings and descriptions herein. Although each of the objects of theinvention is believed to be attained in at least one embodiment of theinvention, there is not necessarily any one embodiment that achieves allof the objects of the invention.

SUMMARY OF THE INVENTION

A debris filter in accordance with the present invention comprises (a) ahousing, casing or shell, (b) a filter screen mounted to the housing anddisposed so as to extend across a flow path through the housing, (c) adebris extractor mounted to the housing, and (d) a splitter bar alsomounted to the housing. The debris extractor and the filter screen areso mounted to the housing as to enable rotation of the filter screen andthe debris extractor relative to one another. The debris extractor has adebris intake opening and the debris extractor and the splitter bar areso mounted to the housing that the intake opening is positionableadjacent to or in juxtaposition with the splitter bar with the splitterbar overlapping and shielding the intake opening.

It is contemplated that the filter screen is spherical, the intakeopening extends along a cylindrical or circular periphery of the debrisextractor, and the splitter bar has a cylindrical or circular innerperiphery juxtaposable to the intake opening.

Pursuant to another feature of the present invention, the splitter barextends across the flow path through the housing, upstream of the filterscreen.

The splitter bar preferably has a tapered or wedge-shaped form. In thatcase, the splitter bar may have a chevron-shaped cross-section. Morespecifically, the splitter bar may include a pair of legs or panels inthe form of webs that are connected to one another along an apical edgeand that diverge from one another away from that apical edge. Inaddition, the webs have respective inner edges opposite the apical edge,the respective edges defining the cylindrical or circular innerperiphery of the splitter bar.

Pursuant to further features of the present invention, the filter screenis mounted to the housing via a connector ring fixed to an inner surfaceof the housing, while the debris extractor is mounted to the housing forrotation about an axis oriented transversely to the path of fluid flowthrough the housing. Also, in a preferred embodiment the filter screenand the splitter bar are fixed relative to the housing, while the debrisextractor is mounted to the housing upstream of an annular upstream edgeof the filter screen.

Where the filter screen defines a filter zone, the debris extractor ispositionable upstream of the filter screen and outside of the filterzone when the intake opening is disposed in juxtaposition with oradjacent to the splitter bar.

The debris extractor preferably includes a plurality of wiper bladesdisposed alongside the intake opening. The splitter bar is so mounted tothe housing that the intake opening is positionable adjacent thesplitter bar with the splitter bar overlapping and shielding the wiperblades.

In accordance with another feature of the present invention, the filterscreen is provided with a plurality of ribs. The preferably take theform of elongate webs extending as annular sections disposed in mutuallyparallel planes on an inner or upstream side of the filter screen.

Where the filter screen is concave and defines a filter zone on anupstream side, the filter zone being bounded by a plane on an upstreamside, the debris extractor has a rest position on a side of the planeopposite the filter screen, so that in the rest position the debrisextractor is disposed outside of the filter zone.

Pursuant to an additional feature of the present invention, the splitterbar has a degree of sharpness selected in accordance with a rate of flowthrough the debris filter, to reduce turbulence around the debris intakeopening of the debris extractor and concomitantly to reduce turbulenceentering the filter zone.

The present invention is also directed to a method for operating adebris filter that includes a filter screen defining a filter zone, thefilter zone being bounded on a downstream side by the filter screen andon an upstream side by a plane passing through an upstream edge of thefilter screen. The method comprises (i) during normal operation of thedebris filter, guiding a fluid stream along a flow path through thefilter screen, (ii) during such normal operation, disposing a debrisextractor in a rest position on an upstream side of the filter screenand outside of the filter zone, (iii) during a cleaning operation,moving the debris extractor from the rest position to a work positioninside the filter zone, and (iv) subsequently during the cleaningoperation, operating the debris extractor to remove debris from insidethe filter zone.

Where the debris filter is provided with a splitter bar mounted to ahousing of the debris extractor, disposed upstream of the filter zoneand extending across the flow path, the disposing of the debrisextractor in the rest position includes juxtaposing a debris intakeopening of the debris extractor to the splitter bar so that the splitterbar shields the intake opening.

Where the debris extractor is rotatably mounted to the housing, themoving of the debris extractor includes rotating the debris extractorabout an axis located upstream of the filter zone and orientedtransversely to the flow path.

In a debris filter in accordance with the present invention, thespherical filter screen and the parking of the debris extractor outsideof the filter zone increases the open area of the filter and allows fora freer flow of water through the system than in conventional debrisfilters. The increase in open area allows for a smaller shell diameterfor a given flow rate. This enables a reduction in equipment cost.Alternatively, a higher flow rate may be supported with the same shelldiameter as in conventional debris filters.

The splitter bar of the present invention protectors the debrisextractor and the rotor wipers while adding shell rigidity andstraightening flow through the filter.

Another advantage of the present invention is a simplified shellconstruction owing to a simplified mounting system for the filterscreen. The use of a mounting ring reinforces the filter shell, housingor casing, enhancing shell rigidity, while providing a simplifiedattachment of the filter screen to the shell.

The screen ribs in a debris filter in accordance with the presentinvention act as flow straighteners that assist in transporting lessturbulent flow through the screen

The present invention contemplates a debris filter with a sphericalfilter screen. A spherical screen offers a more efficient use of spaceand greater inherent open area.

The present invention is directed to a debris filter

The preferred spherical shape of a debris filter in accordance with thepresent invention allows for larger bypass openings that in an emergencyallow more cooling water through the system should the screen becomefully fouled.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front elevational view of a debris filter in accordance withthe present invention.

FIG. 2 is a top plan view of the debris filter of FIG. 1.

FIG. 3 is a right side elevational view of the debris filter of FIGS. 1and 2.

FIG. 4 is a cross-sectional view of the debris filter of FIGS. 1-3,taken along line IV-IV in FIG. 1.

FIG. 5 is a cross-sectional view of the debris filter of FIGS. 1-4,taken along line V-V in FIG. 3.

FIG. 6 is an isometric sectional view of the debris filter of FIGS. 1-5,corresponding to the cross-sectional view of FIG. 4.

FIG. 7 is an isometric sectional view of the debris filter of FIGS. 1-6,corresponding to the cross-sectional view of FIG. 5.

DETAILED DESCRIPTION OF THE INVENTION

A debris filter 10 comprises a substantially cylindrical housing, shellor casing 12 provided at opposite, conically tapered, ends with anannular inlet flange 14 and an annular outlet flange 16 for coupling theshell or housing to an upstream pipe section (not shown) and adownstream pipe section (not shown), respectively. A spherical filterscreen 18, typically made of stainless steel mesh on a stainless steelframe, is mounted to an inner surface 20 of shell or housing 12 via aconnector ring 22 (FIGS. 4, 6, 7) welded thereto and extends across apath 68 (FIGS. 1, 4) of fluid flow through the debris filter. Filterscreen 18 is concave on an upstream side and defines a filter zone 24(FIG. 4). Filter zone 24 is at least substantially hemi-spherical and isdefined or bounded on an upstream side by a plane 26 defined by aleading circular edge 28 of filter screen 18 or, concomitantly,connector ring 22.

Debris filter 10 further comprises a rotatable debris extractor orscreen cleaner 30 for periodically removing debris that accumulates infilter zone 24. Debris extractor 30 includes a cylindrical supportmember or axle 32, a generally semi-circular suction channel 34, andthree tubular mounts 36, 38 and 40 that connect suction channel 34 tosupport member or axle 32.

Support member or axle 32 is mounted to shell or housing 12 via ringbearings 42 and 44 for rotation about an axis 45 (FIG. 5). At one endsupport member or axle 32 is connected to a rotary drive (not shown) viaa coupling 46. An opposite end 48 of support member or axle 32 serves asa debris discharge outlet.

Suction channel 34 has a debris intake opening 50 (FIGS. 4, 6) extendingalong a cylindrical or circular periphery or outer side of the debrisextractor 30. Suction channel 34 has sidewalls 52 (FIGS. 4, 6) thatserve as wiper blades. Sidewalls 52 have circular outer edges 35 spacedfrom one another. Debris intake opening 50 is an elongate gap thatextends lengthwise, in a circumferential dimension, parallel to circularouter edges 35 (FIGS. 4-7) of sidewalls 52 and widthwise between outeredges 35. Edges 35 thus define debris intake opening 50.

Suction channel 34 may be formed internally with partitions 54 and 56(FIGS. 5, 7) that divide the channel into three suction zones 58, 60 and62 (FIGS. 5, 7) that communicate with support member or axle 32 viatubular mounts 36, 38 and 40, respectively.

Filter screen 18 is provided on its inner or concave side with aplurality of ribs 64 in the form of semi-annular webs. Ribs 64 extendparallel to one another and parallel to rotation axis 45 of debrisextractor 30. Thus, ribs or webs 64 extend as annular sections disposedin mutually parallel planes on an inner or upstream side of filterscreen 18.

Debris filter 10 further comprises a splitter bar or beam 66 that, likedebris extractor 30, extends basically transversely across shell orhousing 12 and transversely to path 68 of fluid flow through the debrisfilter. Splitter bar 66 is firmly secured at opposite ends to innersurface 20 of shell or housing 12. Splitter bar 66 has a chevron-shapedcross-section (see FIGS. 4 and 6) and includes a pair of generallysemi-circular legs 70 and 72 in the form of webs connected to oneanother along a semi-circular apical edge 74 and diverging from oneanother away from the apical edge. Legs or webs 70 and 72 haverespective inner edges 76 and 78 opposite apical edge 74, where theinner web edges 76 and 78 together define a cylindrical or circularinner periphery of splitter bar 66. splitter bar 66 may be alternativelyformed with a triangular cross-section (including a third web, notshown, extending between inner edges 76 and 78) or as a solid arcuatewedge.

FIGS. 6-7 depict debris extractor 30 disposed in a parking or restposition. In this rest position, debris extractor is located outside offilter zone 24, away from and upstream of filter screen 18. Debrisintake opening 50 is disposed adjacent to the inner periphery ofsplitter bar 66. (“Inner periphery” means on the concave side ofsplitter bar 66 and also on a side closer to axis 45.) Splitter bar 66thus overlaps intake opening 50 and wiper blades 52, to shield intakeopening 50 and wiper blades 52 from passing debris. The angled ortapered form of splitter bar 66 splits incoming fluid flow, divertingthe flow around debris extractor 30. Splitter bar 66 may be providedwith a profile that is suited for reducing turbulence. Generally, thehigher the expected flow rate, the steeper or sharper the profile ofsplitter bar 66.

When filter zone 24 has accumulated so much debris that the flow rate isimpaired, debris extractor 30 is rotated about axis 45 and into zone 24for cleaning filter screen 18 pursuant to conventional techniques. Atthe end of the cleaning operation, debris extractor is rotated into theparking or rest position behind or downstream of splitter bar 66, asshown in FIGS. 4-7.

Debris filter 10 is used to filter solid particles from liquids,especially for use in steam condensers and heat exchanger in thermal andnuclear power plants. Debris extractor 30 is rotatably driven over theentire surface of filter screen 18 to create a low pressure betweensuction channel 34 and the filter screen for complete extraction ofdebris and conveyance thereof out of the debris filter 10 via supportmember or axle 32.

Splitter bar 66 protects debris extractor 30 and particularly wiperblades 52 thereof from flowing debris. The parking of debris extractor30 upstream of filter screen 18 and outside of filter zone 24 keeps thatzone open. Filter zone 24 is the area of highest speed flow in the pipesystem, logically with the highest concentration of debris. Leaving moreopen flow area in filter zone 24 helps maintain smoother flow andenhanced system performance.

Splitter bar 66 also acts as a flow straightener, thus maintaining ahigh level of system performance. In addition, splitter bar 66incidentally serves as a cross-brace to filter shell or housing 12,thereby augmenting shell stiffness.

Spherical filter screen 18 is easier to fabricate and mounting thanconventional cylindrical filter screens. In addition, it is easier torubber line connector ring 22.

Circular or annular connector ring 22 has a beneficial effect of furtherenhancing the stiffness of shell or housing 12, helping to counteract“hour glassing” during hydro-testing of the unit.

The parking of debris extractor 30 outside of filter zone 24 increasesthe open area of filter zone 24, allowing for smaller shell diameter—amore compact design reducing fabrication costs and space requirements.The hemi-spherical shape of filter screen 18 more closely follows thenatural parabolic flow profile of water. This means that the surface offilter screen 18 is more perpendicular to the flow in areas of greaterflow velocity. This results in the most efficient part of filter screen18 being placed where it is needed the most—in the center of the pipe.

The material of filter screen 18 may be fabricated as “flat” plates asshown or, alternatively, the screen material may be formed in bent(“convoluted”) sections similar to the those used in the current halfround debris filter design (cylindrical screen cross-section) for evenmore available open flow area. Either way the screen frame and screeningmaterial will form a debris collection “pocket”.

It is to be noted that in a debris filter with a spherical filterscreen, one may execute the cleaning function by rotating the filterscreen relative to the debris extractor, which in this case is heldfixed relative to the shell or housing.

It is to be further noted that a spherical screen can be used in both adebris filter as described herein and alternatively modified foroperation in the ball strainer function of a tube cleaning system. Thecurrent standard strainer design is to use two opposed flat screens thatare angled at 20, 25, or 30 degrees relative to the axis of the processpipe. These screens focus the cleaning balls to two points on theoutside of the shell for discharge to a remote ball collector. Whendifferential pressure across the screens increases, they are rotated toallow a backwash cycle. The spherical design would allow for the use ofscreens similarly shaped to the spherical debris filter, but they wouldbe split in the middle and allowed to “clam-shell” for similarbackwashing operation. During ball extraction, however, the screenswould benefit the system by the ability to focus the balls to acentrally located extraction point in the middle of the process pipe.The centrally located, single discharge point would simplify externalpiping and reduce the required number of valves, etc. required to pipethe balls to the ball collector. This arrangement would also allow forthe use of the system for collection of any particle (coarse, fibrous,hard, soft, rubber/polymer, spherical/non-spherical, etc.) Further, byeliminating the need for side baffles (such as those used in the flatplate design), the spherical screens would aid in minimizing ball lossby reducing gaps and points of turbulence.

Although the invention has been described in terms of particularembodiments and applications, one of ordinary skill in the art, in lightof this teaching, can generate additional embodiments and modificationswithout departing from the spirit of or exceeding the scope of theclaimed invention.

For instance, cylindrical support member or axle 32 may be connected tocircular suction channel 34 by one or more tubular mounts, depending onthe size of the debris filter unit. The number of suction zones 58, 60,& 62 will difference concomitantly. Thus, depending on the number oftubular mounts or connecting arms (36, 38, 40), there will be one (1) ormore suction zones (58, 60, 62).

It should be understood that shell or housing 12 can take virtually anyform, in addition to the cylindrical body with tapered ends illustratedin the drawings. Other possible configurations include a straightcylindrical section without tapered ends, a cylindrical section flangedon one end and welded on the other, a cylindrical elbow section havingthe debris filter incorporated into the elbow, and countless otherin-line pipe shell configurations.

It is to be further understood that the method of parking a debrisextractor frame outside of the filter zone of a debris filter may beused with filter screens other than spherical ones. In a debris filterwith a semi-cylindrical screen, the splitter bar has a linear formrather than that of a circular or annular section as in the sphericaldebris filter illustrated herein. In any case, the debris extractor isparked upstream of the filter zone during normal filter operation, asplitter beam fixed to the filter shell or housing upstream of theparked debris extractor serving to divert incoming fluid away from thedebris intake opening of the extractor and smoothly guide the fluid tothe filter screen.

Accordingly, it is to be understood that the drawings and descriptionsherein are proffered by way of example to facilitate comprehension ofthe invention and should not be construed to limit the scope thereof.

What is claimed is:
 1. A debris filter comprising: a housing having aninlet and an outlet defining a flow path through said housing from saidinlet to said outlet; a filter screen fixedly mounted to said housingand disposed so as to extend across said flow path between said inletand said outlet; and a debris extractor rotatably mounted to saidhousing upstream of said filter screen for rotation about a rotationaxis relative to said housing and said filter screen, said debrisextractor having a debris intake opening with an elongate dimension orlength, said filter screen being in the form of a spherical sectionhaving an axis of symmetry, said elongate dimension or length of saidintake opening extending along a cylindrical or circular periphery ofsaid debris extractor, said rotation axis being located in a planeextending perpendicularly to said axis of symmetry.
 2. The debris filterdefined in claim 1, further comprising a splitter bar mounted to saidhousing so as to extend across said flow path upstream of said filterscreen, said splitter bar having a cylindrical or circular innerperiphery juxtaposable to the intake opening so that rotation of saiddebris extractor can position said intake opening in juxtaposition withor adjacent to said splitter bar and in parallel relation thereto withsaid splitter bar overlapping and shielding said intake opening.
 3. Thedebris filter defined in claim 2 wherein said splitter bar has a taperedor wedge-shaped form.
 4. The debris filter defined in claim 3 whereinsaid splitter bar has a chevron-shaped cross-section.
 5. The debrisfilter defined in claim 4 wherein said splitter bar includes a pair oflegs in the form of webs connected to one another along an apical edgeand diverging from one another away from said edge, said webs havingrespective edges opposite said apical edge, said respective edgesdefining said cylindrical or circular inner periphery of said splitterbar.
 6. The debris filter defined in claim 2 wherein said filter screenis mounted to said housing via a connector ring fixed to an innersurface of said housing.
 7. The debris filter defined in claim 2 whereinsaid rotation axis is oriented transversely to said path of fluid flowthrough said housing, said splitter bar being fixed relative to saidhousing.
 8. The debris filter defined in claim 7 wherein said debrisextractor is mounted to said housing upstream of an annular upstreamedge of said filter screen.
 9. The debris filter defined in claim 2wherein said filter screen defines a filter zone, said debris extractorbeing positionable upstream of said filter screen and outside of saidfilter zone when said intake opening is disposed adjacent said splitterbar.
 10. The debris filter defined in claim 2 wherein said debrisextractor includes a plurality of wiper blades disposed alongside saidintake opening, said splitter bar being so mounted to said housing thatsaid intake opening is positionable adjacent said splitter bar with saidsplitter bar overlapping and shielding said wiper blades.
 11. The debrisfilter defined in claim 2 wherein said splitter bar has an upstreamsurface, facing away from said filter screen, said upstream surfacehaving a wedge or chevron shape with legs at an angle selected inaccordance with a rate of flow through said debris filter, to reduceturbulence around said debris intake opening of said debris extractorand concomitantly to reduce turbulence entering said filter zone. 12.The debris filter defined in claim 2 wherein said splitter bar has atapered or wedge-shaped form.
 13. The debris filter defined in claim 2wherein said splitter bar has a chevron-shaped cross-section.
 14. Thedebris filter defined in claim 2 wherein said splitter bar includes apair of legs in the form of webs connected to one another along anapical edge and diverging from one another away from said edge, saidwebs having respective edges opposite said apical edge, said respectiveedges defining said cylindrical or circular inner periphery of saidsplitter bar.
 15. The debris filter defined in claim 1 wherein saidfilter screen is concave and defines a filter zone on an upstream side,said filter zone being bounded by a plane on an upstream side, saiddebris extractor having a rest position on a side of said plane oppositesaid filter screen, so that in said rest position said debris extractoris disposed outside of said filter zone.
 16. The debris filter definedin claim 1 wherein said filter screen is mounted to said housing via aconnector ring fixed to an inner surface of said housing.
 17. A debrisfilter comprising: a housing having an inlet and an outlet defining aflow path through said housing from said inlet to said outlet; a filterscreen fixedly mounted to said housing and disposed so as to extendacross said flow path between said inlet and said outlet; and a debrisextractor rotatably mounted to said housing upstream of said filterscreen for rotation about an axis relative to said housing and saidfilter screen, said debris extractor having a debris intake opening withan elongate dimension or length, said filter screen being in the form ofa spherical section, said an elongate dimension or length of said intakeopening extending along a cylindrical or circular periphery of saiddebris extractor, wherein said filter screen is provided with aplurality of ribs, said ribs being elongate webs extending as annularsections disposed in mutually parallel planes on an inner or upstreamside of said filter screen.
 18. A method for operating a debris filterincluding a filter screen in the form of a spherical section defining afilter zone, said filter screen having an axis of symmetry, said filterzone being bounded on a downstream side by said filter screen and on anupstream side by a plane passing through an upstream edge of said filterscreen, said method comprising: during normal operation of the debrisfilter, guiding a fluid stream along a flow path through said filterscreen; during such normal operation, disposing a debris extractor in arest position on an upstream side of said filter screen and outside ofsaid filter zone; during a cleaning operation, moving said debrisextractor from said rest position to a work position inside said filterzone, the moving of said debris extractor including rotating said debrisextractor about a rotation axis disposed in a plane orientedperpendicularly to said axis of symmetry; and subsequently during saidcleaning operation, operating said debris extractor to remove debrisfrom inside said filter zone.
 19. The method defined in claim 18 whereinsaid debris filter is provided with a splitter bar mounted to a housingof said debris extractor, disposed upstream of said filter zone andextending across said flow path, the disposing of said debris extractorin said rest position including juxtaposing a debris intake opening ofsaid debris extractor to said splitter bar so that said splitter barshields said intake opening.
 20. The method defined in claim 18 whereinsaid rotation axis is located upstream of said filter zone and orientedtransversely to said flow path.